The present invention relates generally to security systems. More particularly, it relates to security systems for limiting access to such diverse places and things as private or public premises, safes, security areas in buildings, electrical devices, computer terminals, computer programs, and electronically stored information such as credit records, just to mention a few of the applications where security is required.
Many types of access control systems have been devised over the years from the earliest forms of key operated locks, to the sophistication of combination locks and the relatively recent advent of electronically coded card keys and readers. None of these systems has been particularly satisfactory, however, since more and more sophisticated procedures have been developed to defeat them. Keys can be duplicated, combinations can be broken by trial and error or detected by observation of an authorized person opening the combination controlled lock and electronically coded card keys can be forged.
For example, there are a variety of computer-controlled password locks commercially available on the market, such as a computer-controlled lock system disclosed in U.S. Pat. No. 3,953,769 to Sopko, wherein a keyboard is mounted on the outside of a door and is connected to computer-controlled circuitry enclosed in a housing mounted on the inside of the door to control energization of a deadbolt solenoid. The lock system permits a user to open the lock by keying in a correct numeral password from its keyboard, thereby preventing it from being opened with a master key by a thief. With such a computer-controlled lock, the user need not bring a key with him, so that it is not only convenient, but also able to eliminate the possibility of losing the key. In addition, the user can reset the password of the lock as desired, and thus need not worry about anybody, including the one who sells the lock, being aware of the password. Although conventional computer-controlled password locks have the above advantages, they still have several drawbacks, such as the user must memorize a password of four or more figures, and that the length of the password cannot be adjusted. In addition, since the user frequently selects his birthday, part of his telephone number or identification card number, or the like as the password to facilitate memorization, somebody who familiarizes himself with the user may guess at the password.